Back pain can be caused by a variety of factors, including, but not limited to the rupture or degeneration of one or more intervertebral discs due to degenerative disk disease, spondylolisthesis, deformative disorders, trauma, tumors and the like. In such causes, pain typically results from compression or irritation of spinal nerve roots by reduced spacing between adjacent vertebrae, a damaged disk and/or misalignment of the spine resulting of the injury or degeneration.
Common forms of treating such pain include various types of surgical procedures that include mounting a plate across two or more adjacent vertebrae to stabilize them, including, but not limited to aligning the vertebrae to alleviate pain and achieve bony fusion between said vertebrae. After installation of such a plate, once the patient has recovered to the extent where the patient can at least sit upright, the gravitational forces on the spine typically cause some subsidence forces to be applied to the treated vertebrae, particularly in cases where one or more grafts have been placed between one or more pairs of adjacent vertebrae. Greater amounts of subsidence that what normally occurs (as described above) can result from inadequate grafting technique, poor graft quality and/or poor bone quality (e.g., osteoporosis).
Current plate systems do not provide a screw-plate interface that is adequate to account for the subsidence that occurs. Specifically, current systems do not allow sufficient angulation of the screws relative to the plane of the plate to allow the screws to be oriented as needed during the initial anchoring of the plate to the vertebrae. Further, many current systems do not allow axial movement of the screws relative to the longitudinal axis of the plate to further accommodate subsidence.
There is a continuing need for plates and plate systems that allow improved angulation of screws relative to the face or plane of the plate. There is a continuing need for plates and plates systems that include dynamic features that allow for axial changes in positioning of one or more screws relative to the longitudinal axis or length dimension of the plate that they are installed through, to dynamically accommodate subsidence. The present invention meets at least all of the above needs.